Santa Claus

Santa Claus is an NPC added in the 1.1.1 update obtained after completing the Frost Legion event triggered by a Snow Globe. Santa Claus is only available during Dec. 15 - 31st each year, as stated by Re-Logic in the release notes. As of the 1st of January every year, Santa Claus will no longer be available until the next Christmas period. Existing Santa NPCs will either despawn or die, indicated by a 'Santa was slain' message. However, if you set your computer time to a time between Dec. 15-31st, he will respawn.

Quotes

What? You thought I wasn't real?

Care to bake me some cookies?

Ho ho ho, and a bottle of... Egg Nog!

Notes

Santa Claus is the only town-based NPC who doesn't receive a randomly generated name.

Technically, Santa Claus can be called a Named NPC. This is because his NPC flag (When placed in a player's house) has the caption: "Santa Claus the Santa Claus." By some, this could be considered a bug.

Santa Claus increases the drop rate of gifts in a radius of 50 blocks.

On the IOS version, if you updated your game to the Christmas update, he will spawn no matter what.